Theses and Dissertations

Date of Award

7-2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Dr. Wei Lin

Second Advisor

Dr. Shervin Fatehi

Third Advisor

Dr. Evangelia Kotsikorou

Abstract

The first chapter of this thesis introduces the basic theory of rotational spectroscopy. This includes the theory of a rigid rotor, centrifugal distortion, and hyperfine effects. The theory behind diatomic systems is explained first, and then expanded to the asymmetric top system. The second chapter encompasses a brief overview on the development of microwave spectroscopy and discusses the instruments that were utilized during this study, namely the cavity-based and chirped-pulse Fourier transform microwave spectrometers. Chapter three describes the quantum chemical calculation methods and basis sets that were applied throughout this study. Chapter four discusses the progress of data analysis of the rotational spectrum of 1,1-diiodoethane. Only a few molecules with two iodine atoms have been studied using rotational spectroscopy. This is due to the complex hyperfine splitting structure arising from the presence of two iodine nuclei. The analysis was aided by quantum chemical calculations. A potential energy surface scan was performed at the MP2/aug-cc-pVTZ-pp level to acquire the lowest energy conformation of 1,1-diiodoethane and to help estimate the V3 barrier height. Ab initio calculations were carried out on the global minimum conformation at the CCSD(T) and MP2 levels along with the aug-cc-pVTZ-pp basis set, in order to help predict the molecular geometry and the hyperfine parameters. We report the high resolution rotational spectroscopic observation of the 1,1-diiodoethane for the first time. The spectrum was observed at 11-18 GHz frequency range in a jet-pulsed cavity-based Fourier transform microwave spectrometer. The observed transition frequencies were analyzed to yield the rotational constants, centrifugal distortion constants, the nuclear quadrupole coupling constants, and nuclear-spin rotation constants. Previous literature shows that molecules with a terminal methyl group may undergo internal rotation. The experimental spectrum of 1,1-diiodoethane seems to indicate that there is internal rotation. Although with our preliminary fit this cannot be concluded for sure.

Comments

Copyright 2020 Michael Joseph Carrillo. All Rights Reserved.

https://go.openathens.net/redirector/utrgv.edu?url=https://www.proquest.com/dissertations-theses/rotational-spectrum-1-diiodoethane/docview/2454687018/se-2?accountid=7119

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